Colored transparent, translucent and opaque glass-ceramics

ABSTRACT

This invention is directed to the production of transparent, translucent, and opaque glass-ceramic articles containing β-quartz solid solution as the predominant crystal phase exhibiting colors ranging from black to brown to red, and opaque glass-ceramic articles containing β-spodumene solid solution as the predominant crystal phase exhibiting colors ranging from gray to brown to almond to beige to yellow to blue. Both types of articles can be prepared by heat treating precursor glass articles essentially free from MgO and consisting essentially, in weight percent, of: 
     
         ______________________________________                                    
 
    
     SiO 2                                                                  
         63.5-69      BaO     0-5                                         
Al 2  O 3                                                           
         15-25        TiO 2                                            
                              &gt;2.5-6                                      
Li 2  O                                                                
         2.5-4        ZrO 2                                            
                              0-2                                         
Na 2  O                                                                
         0.1-0.6      As 2  O 3                                     
                              0.4-0.8                                     
K 2  O                                                                 
         0.1-0.6      Fe 2  O 3                                     
                              0.05-0.2                                    
ZnO      0-2                                                              
______________________________________                                    
 
     and 0.3-3% total of at least two oxides in the indicated proportions selected from the group of 0-2% CaO, 0-3% CeO 2 , 0-1% NiO, 0-1.5% SnO 2 , 0-0.3% V 2  O 5 , and 0-1% WO 3 . The articles can be made resistant to attack by the atmosphere generated in a coal or wood burning stove by subjecting the surface thereof to an ion exchange reaction where Li +  ions in the crystals are replaced with K +  ions.

This application is a continuation-in-part of application Ser. No. 451,284, filed Dec. 20, 1982, now abandoned.

BACKGROUND OF THE INVENTION

U.S. application Ser. No. 451,283, filed concurrently to Ser. No. 451,284 by me under the title Transparent Colorless Glass-Ceramics Especially Suitable for Use as Stove Windows, discloses a relatively narrow range of precursor glass compositions which, although containing TiO₂ and up to 0.1% by weight Fe₂ O₃, can surprisingly be crystallized in situ through heat treatment to yield essentially colorless glass-ceramic articles wherein β-quartz solid solution constitutes the predominant crystal phase. Thus, as is discussed therein, in crystallizing the typical parent glass article containing TiO₂ as a nucleating agent and Fe₂ O₃ as an impurity in amounts greater than 0.01%, a reaction is believed to take place between the titanium and iron ions during the heat treatment process, whereby the valence state of the titanium ions is reduced from +4 to +3. The result of that reaction is the formation of an unattractive gray-brown coloration in the glass-ceramic. The crux of that inventive subject matter lies in the discovery that the essential absence of MgO from the compositions permits the production of virtually colorless, transparent glass-ceramic bodies from precursor glasses containing up to 0.1% Fe₂ O₃, wherein TiO₂ comprised at least a substantial portion of the nucleating agent. And, because β-quartz or β-eucryptite solid solution crystals, as such have been variously denominated, can exhibit coefficients of thermal expansion over the range of 0°-300° C. of 0 or less, those glass-ceramics can demonstrate coefficients of thermal expansion over the same temperature interval within the regime of about -10 to +10×10⁻⁷ /°C. Those glass-ceramic articles are produced by heat treating the following glass compositions, expressed in terms of weight percent on the oxide basis, at temperatures between about 750°-950° C.:

    ______________________________________                                         SiO.sub.2      65-75                                                           Li.sub.2 O     1-4                                                             Al.sub.2 O.sub.3                                                                              15-25                                                           ZnO            0.5-2                                                           Na.sub.2 O and/or K.sub.2 O                                                                   0-2                                                             TiO.sub.2      2-6                                                             ZrO.sub.2      0-2                                                             BaO            0-2                                                             F                0-1.2                                                         Fe.sub.2 O.sub.3                                                                              >0.01 but <0.1                                                  ______________________________________                                    

The most preferred composition was stated to have an analyzed composition of about:

    ______________________________________                                                 SiO.sub.2                                                                            66.6%                                                                    Al.sub.2 O.sub.3                                                                     20.5                                                                     Li.sub.2 O                                                                           3.7                                                                      Na.sub.2 O                                                                           0.4                                                                      K.sub.2 O                                                                            0.5                                                                      ZnO   1.0                                                                      BaO   2.0                                                                      TiO.sub.2                                                                            2.6                                                                      ZrO.sub.2                                                                            1.6                                                                      As.sub.2 O.sub.3                                                                     0.5                                                                      Fe.sub.2 O.sub.3                                                                     0.05                                                             ______________________________________                                    

Those glass-ceramics are described as being especially useful as windows for coal and wood burning stoves since their transparency and lack of color provided an uninterrupted and undistorted view of the fire inside the stove. However, because the precursor glass therefor possesses the thermal stability and viscosity characteristics necessary for forming sheet, coupled with their high refractoriness, excellent chemical durability, very low coefficient of thermal expansion (about ±7×10⁻⁷ /°C. over the range of 25°-700° C.), and capability of being crystallized in situ very rapidly, other applications for those glass-ceramics in sheet form such as countertops and range tops have become apparent.

As can be appreciated, not all such applications require a colorless transparent product. Indeed, where a decorative effect is wanted, colors immediately come to mind. (Even in windows for coal and wood burning stoves, there has been some desire voiced for a product having a light brown tint to impart a warm, cheerful appearance to the fire inside.) Furthermore, many applications do not require transparent products. Accordingly, it would be highly desirable to be able to produce transparent and opaque glass-ceramic articles having compositions approximating the analyzed values above, but exhibiting a range of colors.

SUMMARY OF THE INVENTION

Transparent, translucent, and opaque glass-ceramic articles containing β-quartz solid solution as the predominant crystal phase exhibiting colors ranging from black to brown to red, and opaque glass-ceramic articles containing β-spodumene solid solution as the predominant crystal phase exhibiting colors ranging from gray to brown to almond to beige to yellow to blue can be prepared from precursor glasses having base compositions essentially free from MgO consisting essentially, in weight percent, of:

    ______________________________________                                                SiO.sub.2                                                                            63.5-69                                                                  Al.sub.2 O.sub.3                                                                     15-25                                                                    Li.sub.2 O                                                                           2.5-4                                                                    Na.sub.2 O                                                                           0.1-0.6                                                                  K.sub.2 O                                                                            0.1-0.6                                                                  Zno   0-2                                                                      BaO   0-5                                                                      TiO.sub.2                                                                            2-3                                                                      ZrO.sub.2                                                                            0.5-2.5                                                                  As.sub.2 O.sub.3                                                                     0.4-0.8                                                                  Fe.sub.2 O.sub.3                                                                     0.05-0.1                                                          ______________________________________                                    

The desired colors are obtained through the use of a "color package" containing about 0.5-3% TiO₂ and up to 0.15% Fe₂ O₃ with 0.3-3% total of at least two oxides in the indicated proportion selected from the group of up to 0.3% V₂ O₅, up to 3% CeO₂, up to 2% CaO, up to 1% NiO, up to 1% WO₃, and up to 1.5% SnO₂. The total TiO₂ content will range >2.5-6% and the Fe₂ O₃ content will range 0.05-0.2%.

The means for making the inventive products comprises three general steps:

(a) a batch for a glass having a composition within the above ranges is melted;

(b) the melt is simultaneously cooled to a temperature at least below the transformation range thereof and a glass article of a desired configuration shaped therefrom; and

(c) the glass article is heat treated in a manner to cause the crystallization in situ thereof.

Where a glass-ceramic article containing β-quartz solid solution as the predominant crystal phase is desired, the precursor glass article will be heat treated at temperatures between about 750°-950° C. for a time sufficient to effect crystallization in situ. Where an article containing β-spodumene solid solution as the predominant crystal phase is desired, the precursor glass article will be heat treated at temperature between about 950°-1150° C. for a time sufficient to cause crystallization in situ.

Each of the above-delineated members of the "color package" displays a tendency to raise the coefficient of thermal expansion of the base composition, especially when heat treated to effect crystallization of beta-spodumene solid solution. To illustrate, the coefficients of thermal expansion of such glass-ceramic bodies can be readily raised from the customary 6-8×10⁻⁷ /°C. to >10×10⁻⁷ /°C. (25°-700°) when the coloring oxides are incorporated. Consequently, it is essential that the concentrations of the "color package" ingredients be kept to a minimum, while still obtaining the desired tints, in order to secure the most thermally stable, crystallized articles.

It is possible to offset at least a portion of that increase in thermal expansion by varying the amounts of the components of the base composition. For example, utilizing levels of BaO, CaO, Na₂ O, K₂ O, Al₂ O₃, TiO₂, and As₂ O₃ at the lower end of the operable ranges thereof, when possible, will reduce the coefficient of thermal expansion of a beta-spodumene solid solution-containing glass-ceramic. Further, the substitution of SnO₂ for the combination of CeO₂ +CaO substantially decreases the thermal expansion of those articles.

Finally, it is possible to make small additions, viz., no more than a total of about 3%, of such oxides as Cu₂ O, La₂ O₃, B₂ O₃, and Cs₂ O and the transition metal oxides CoO, MnO, Cr₂ O₃, and Nb₂ O₅ without seriously altering the colors and physical properties desired. In general, individual values of each addition will be held below 1%. MgO exerts a deleterious effect upon the colors produced (haze develops in transparent articles and the colors are not as intense in the opaque bodies), so no more than 0.5% can be tolerated and, preferably, the compositions will be essentially free from MgO.

The exact mechanism operating to produce the inventive coloration is not known with certainty but it is believed that the TiO₂ and Fe₂ O₃ react with the other members of the "color package" and/or the above-cited transition metal oxides. Hence, as was disclosed in Ser. No. 451,283, the reaction deemed to take place between titanium and iron ions during the crystallization heat treatment, whereby the valence state of the titanium ions is reduced from +4 to +3, results in the development of an unattractive gray-brown coloration in the transparent glass-ceramic. Because of the relatively wide palette of colors which can be generated in the inventive glass-ceramics, it is believed apparent that a further and/or different reaction must be taking place during the crystallization heat treatment involving the other "color package" components and the transition metal oxides when present.

The presence of As₂ O₃ in the composition leads to the development of more intense colors. The mechanism underlying this phenomenon is also not understood, but the inclusion of about 0.4-0.6% As₂ O₃ is preferred to intensify the coloration generated.

U.S. application Ser. No. 451,282, filed concurrently to Ser. No. 451,284 by me under the title Transparent Glass-Ceramics Especially Suitable for Use as Stove Windows, discloses means by which glass-ceramic articles containing β-quartz solid solution as the predominant crystal phase and having compositions within two regimes of components can be made exceptionally resistant to attack by the atmosphere generated in a coal or wood burning stove.

In the first embodiment of that inventive method the precursor glass article is initially exposed to a H⁺ ion and Li⁺ ion exchange reaction utilizing the practice generally disclosed in U.S. Pat. No. 3,834,981, i.e., by immersion into a bath of strong mineral acid at temperatures of about 25°-320° C. to remove Li⁺ ions from the glass surface to a depth of at least 10 microns and preferably 25 microns. Thereafter, the glass article is heat treated to be crystallized in situ to a glass-ceramic containing β-quartz solid solution as the predominant crystal phase. The ion exchange reaction must be carried out on the parent glass article because crazing occurs when the glass-ceramic article is subjected to the H⁺ ion for Li⁺ ion exchange reaction.

In the second and preferred embodiment of that inventive method, the precursor glass article is first heat treated to be crystallized in situ to a glass-ceramic containing β-quartz solid solution as the predominant crystal phase. Thereafter, the glass-ceramic article is subjected to a K⁺ ion for Li⁺ ion exchange reaction by contact with a source of K⁺ ions (customarily a bath of a molten potassium salt) at temperatures between about 400°-800° C. for a period of time sufficient to cause the replacement of Li⁺ ions in the β-quartz solid solution crystals with K⁺ ions to a depth of at least 10 microns and preferably 25 microns into the surface of the article. A bath of molten KNO₃ is the suggested source of K⁺ ions at temperatures of 400°-600° C. and the eutectic 52% KCl-48% K₂ SO₄ (by weight) as the source at 700°-800° C. The ion exchange must be carried out on the glass-ceramic because, when employed on the precursor glass and the glass then heat treated to be crystallized in situ, crazing always occurs.

Accordingly, where a colored window or other transparent element of a coal or wood burning stove is the desired product, either of the two method embodiments of Ser. No. 451,282 may be applied. For example:

(a) the glass article of the present inventive compositions may be subjected to a H⁺ for Li⁺ ion exchange via immersion into a bath of a strong mineral acid operating at about 25°-320° C. and thereafter crystallized in situ at about 750°-950° C., or

(b) the glass-ceramic article of the present inventive compositions may be subjected to a K⁺ for Li⁺ ion exchange via contact with a source of K⁺ ions about 400°-800° C., the source customarily consisting of a bath of a molten potassium salt.

Glass-ceramic articles containing β-spodumene solid solution as the predominant crystal phase can also be made resistant to the fumes encountered in coal and wood burning stoves utilizing either of the two embodiments of the method disclosed in Ser. No. 451,282. Should such a product be desired, the precursor glass will be crystallized in situ at temperatures between 950°-1150° C., instead of the 750°-950° C. required in the crystallization of β-quartz solid solution.

RELATED APPLICATIONS

Ser. No. 451,282 filed concurrently to Ser. No. 451,284 by me under the title Transparent Glass-Ceramic Especially Suitable for Use as Stove Windows.

Ser. No. 451,283 filed concurrently to Ser. No. 451,284 by me under the title Transparent Colorless Glass-Ceramics Especially Suitable for Use as Stove Windows.

PRIOR ART

U.S. Pat. No. 3,788,865 described colored, transparent glass-ceramic articles containing β-eucryptite or β-spodumene as the predominant crystal phase prepared from precursor glasses having compositions consisting essentially, in weight percent, of:

    ______________________________________                                         SiO.sub.2                                                                            50-75      ZrO.sub.2 + TiO.sub.2 + SnO.sub.2                                                             Not over 10                                    Al.sub.2 O.sub.3                                                                     16-35      Alkaline Earth Oxides                                                                           0-4.5                                        Li.sub.2 O                                                                             3-5.5    SiO.sub.2 + Al.sub.2 O.sub.3                                                                  75-92                                          B.sub.2 O.sub.3                                                                      0-9        ZnO            0-4                                            ZrO.sub.2                                                                            0-5        Na.sub.2 O     0-2                                            TiO.sub.2                                                                             0-10      F.sub.2          0-0.2                                        SnO.sub.2                                                                            0-5        Colorants      0.005-2                                        P.sub.2 O.sub.5                                                                      0-3                                                                      ______________________________________                                    

The colorants included V₂ O₅, MnO, Cr₂ O₃, Fe₂ O₃, CuO, NiO, CuO, and ZnS.

As can be observed, TiO₂ and Fe₂ O₃ are merely optional components and no mention is made of a reaction taking place between those two components and with at least two members of the group CaO, CeO₂, NiO, SnO₂, V₂ O₅, and WO₃. Yet, that reaction comprises the nub of the instant invention. Furthermore, the patent has no description of the facility of As₂ O₃ for enhancing the intensity of the colors developed.

U.S. Pat. No. 3,907,577 disclosed optionally-colored, translucent or opaque glass bodies having a surface compression layer produced via the in situ growth of β-spodumene and/or h-quartz crystals during a heat treatment of the glass bodies. Compositions for the glasses consisted essentially, in weight percent, of:

    ______________________________________                                         SiO.sub.2                                                                              52-70       MgO           0-5                                          Al.sub.2 O.sub.3                                                                       10-25       ZnO           0-7                                          B.sub.2 O.sub.3                                                                        0-8         CaO            0-10                                        P.sub.2 O.sub.5                                                                         0-10       BaO            0-12                                        Li.sub.2 O                                                                             1-4         TiO.sub.2       0-1.2                                      Na.sub.2 O                                                                             0-8         ZrO.sub.2       0-2.5                                      K.sub.2 O                                                                               0-10       Fe.sub.2 O.sub.3 and/or NiO                                                                   0-10                                                            and/or CoO and/or                                                              Cr.sub.2 O.sub.3                                           ______________________________________                                    

The patent has no discussion of the necessary reaction between TiO₂ and Fe₂ O₃ with at least two members of the group CaO, CeO₂, NiO, SnO₂, V₂ O₅, and WO₃. As a matter of fact, the TiO₂ content of the patented glasses is less than one-half of the minimum TiO₂ level demanded in the instant invention. The patent does not even suggest the capability of As₂ O₃ for augmenting the intensity of the colors produced.

U.S. Pat. No. 3,962,514 was concerned with the formation of glass-ceramic bodies containing β-quartz and/or β-spodumene solid solutions as the predominant crystal phase and having an integral, colored surface layer of transition metal spinel crystals. The precursor glass bodies consisted essentially, in weight percent, of:

    ______________________________________                                         SiO.sub.2                                                                              55-80     Transition Metal Oxides                                                                        0.1-10                                       Al.sub.2 O.sub.3                                                                       14-35     TiO.sub.2 + ZrO.sub.2                                                                           3-13                                        Li.sub.2 O                                                                             0-5       ZrO.sub.2        0-10                                        TiO.sub.2                                                                              0-7       F               0-3                                          ______________________________________                                    

The transition metal oxides included 0-5% MnO₂, 0-5% Fe₂ O₃, 0-3%, CoO, 0-2% CuO, 0-2% Cr₂ O₃, 0-3% V₂ O₅, and 0-10% NiO.

There is no indication of any reaction taking place between TiO₂ and Fe₂ O₃ with at least two members of the group CaO, CeO₂, NiO, SnO₂, V₂ O₅, and WO₃ ; and there is no reference made to the operability of As₂ O₃ for intensifying the colors produced.

U.S. Pat. No. 4,007,048 was directed to preparing dark red, transparent glass-ceramic bodies containing h-quartz and/or h-spodumene solid solution as the predominant crystal phase and consisting essentially, in weight percent of:

    ______________________________________                                         SiO.sub.2                                                                              64.00 ± 0.30                                                                               ZnO     1.50 ± 0.50                                  Al.sub.2 O.sub.3                                                                       21.30 ± 0.20                                                                               TiO.sub.2                                                                              2.30 ± 0.10                                  Li.sub.2 O                                                                             3.50 ± 0.15 ZrO.sub.2                                                                              1.60 ± 0.10                                  Na.sub.2 O                                                                             0.60 ± 0.15 MnO.sub.2                                                                              0.65 ± 0.15                                  K.sub.2 O                                                                              0.50 ± 0.10 Fe.sub.2 O.sub.3                                                                       0.23 ± 0.03                                  BaO     2.50 ± 0.50 CoO     0.37 ± 0.05                                  CaO     0.20 ± 0.20 NiO     0.06 ± 0.02                                  MgO     0.10 ± 0.10 Sb.sub.2 O.sub.3                                                                       0.85 ± 0.15                                  ______________________________________                                    

Not only is the TiO₂ content below the minimum required in the instant invention, but also there is no statement of a reaction occurring between TiO₂ and Fe₂ O₃ with at least two members of the group CaO, CeO₂, NiO, SnO₂, V₂ O₅, and WO₃. Nor is there even an allusion to the efficacy of As₂ O₃ for improving the colors generated.

U.S. Pat. No. 4,042,362 was directed to a two-step process for very rapidly converting molten glass into a glass-ceramic body. Whereas the process is not limited to specified compositions, several of the working examples produced glass-ceramic bodies containing β-quartz and/or β-spodumene solid solution as the predominant crystal phase. Colored articles are nowhere referred to and in those examples Fe₂ O₃ is merely an optional ingredient. There is no discussion of any reaction taking place between TiO₂ and Fe₂ O₃ with at least two members of the group CaO, CeO₂, NiO, SnO₂, V₂ O₅, and WO₃, nor any account of the effectiveness of As₂ O₃ in increasing the intensity of the colors developed.

U.S. Pat. No. 4,084,974 was drawn to the preparation of light absorbing glass-ceramic bodies manifesting a blue-to-black coloration and containing β-quartz and β-spodumene solid solution as the predominant crystal phase from base compositions in the Li₂ O-Al₂ O₃ -SiO₂ system nucleated with TiO₂. Fe₂ O₃ is nowhere mentioned so, self-evidently, there was no suggestion of a reaction occurring between TiO₂ and Fe₂ O₃ with at least two members of the group CaO, CeO₂, NiO, SnO₂, V₂ O₅, and WO₃. As₂ O₃ appears in the working examples but there is no statement of its utility in enhancing color intensity.

U.S. Pat. No. 4,211,820 disclosed transparent glass-ceramic articles exhibiting a warm brown coloration and containing β-quartz solid solution as the predominant crystal phase with, optionally, a minor amount of β-spodumene solid solution. The compositions therefor consisted essentially, in weight percent, of:

    ______________________________________                                         Li.sub.2 O                                                                              2.5-4.5       SiO.sub.2                                                                              66.5-68                                         MgO      1-2           TiO.sub.2                                                                              4-5                                             ZnO      1-2           V.sub.2 O.sub.5                                                                        0.02-0.2                                        Al.sub.2 O.sub.3                                                                        19.5-21                                                               ______________________________________                                    

V₂ O₅ was stated to impart the desired color.

Fe₂ O₃ was not intentionally included in the composition but is merely present as an impurity in several of the working examples. There is no discussion of any reaction taking place between TiO₂ and Fe₂ O₃ with at least two members of the group CaO, CeO₂, NiO, SnO₂, V₂ O₅, and WO₃ to yield a wide spectrum of colors. The patented products exhibited a brown coloration only. MgO is a required component of the patented compositions whereas, because of its adverse effect upon the coloration of the instant inventive products, its essential absence is greatly preferred. As₂ O₅ is referred to only as a fining agent; there is no indication of its faculty for enhancing the intensity of a color produced.

DESCRIPTION OF PREFERRED EMBODIMENTS

Table I records a group of exemplary compositions, expressed in terms of parts by weight on the oxide basis, illustrating the compositional parameters of the inventive products. Because the sum of the individual components totals or closely approximates 100, for all practical purposes the values reported may be deemed to represent weight percent. The actual ingredients employed in preparing the batch may comprise materials, either the oxides or other compounds which, when melted together, will be converted into the desired oxide in the proper proportions.

The batch ingredients were compounded, ballmilled together to aid in obtaining a homogeneous melt, the batches deposited into platinum crucibles, lids placed upon the crucibles, and the crucibles introduced into a furnace operating at about 1550°-1600° C. The batches were melted for about 16 hours with stirring, canes having a diameter of about 0.25" were hand-drawn from each melt and the remainder of each melt poured into a steel mold to form a glass slab having dimensions of about 6"×6"×0.5". The slabs were transferred immediately to an annealer operating at about 650°-700° C.

As₂ O₃ is present to perform its customary function of a fining agent as well as to promote the development of more intense colors.

                  TABLE I                                                          ______________________________________                                               1      2      3    4    5    6    7    8    9                            ______________________________________                                         SiO.sub.2                                                                            67.1   67.3   66.0 67.6 67.4 66.3 68.8 68.4 66.8                         Al.sub.2 O.sub.3                                                                     20.0   20.0   20.0 20.0 20.0 21.0 19.0 19.0 19.0                         Li.sub.2 O                                                                           3.8    3.8    3.5  3.8  4.0  3.6  3.8  4.0  3.8                          Na.sub.2 O                                                                           0.3    0.3    0.4  0.3  0.3  0.1  0.3  0.3  0.3                          K.sub.2 O                                                                            0.5    0.5    0.6  0.3  0.3  0.1  0.3  0.3  0.3                          ZnO   0.8    0.8    0.8  0.8  0.8  1.2  0.8  0.8  1.2                          BaO   0.8    0.8    0.8  1.0  0.8  2.5  1.0  0.8  2.5                          TiO.sub.2                                                                            3.2    3.4    4.6  3.4  3.4  3.0  3.4  3.4  3.3                          ZrO.sub.2                                                                            1.6    1.6    1.6  1.6  1.6  1.6  1.6  1.6  1.6                          As.sub.2 O.sub.3                                                                     0.6    0.6    0.6  0.6  0.6  0.4  0.6  0.6  0.6                          Fe.sub.2 O.sub.3                                                                     0.15   0.15   0.15 0.15 0.1  0.15 0.15 0.1  0.15                         V.sub.2 O.sub.5                                                                      0.2    0.2    0.2  0.2  0.2  0.2  0.2  0.2  0.2                          CeO.sub.2                                                                            1.0    0.3    0.8  0.2  0.3  0.1  --   0.3  --                           CaO   --     0.3    --   0.1  0.3  0.3  --   0.3  --                           SnO.sub.2                                                                            --     --     --   --   --   --   0.1  --   0.1                          ______________________________________                                               10     11     12   13   14   15   16   17   18                           ______________________________________                                         SiO.sub.2                                                                            67.4   67.1   68.1 63.9 64.6 66.4 66.4 67.3 66.1                         Al.sub.2 O.sub.3                                                                     19.0   19.0   18.0 20.0 20.0 19.0 19.0 19.0 19.0                         Li.sub.2 O                                                                           3.0    3.5    3.5  3.5  3.5  3.8  3.8  3.8  3.5                          Na.sub.2 O                                                                           0.3    0.3    0.3  0.3  0.3  0.3  0.3  0.3  0.3                          K.sub.2 O                                                                            0.3    0.3    0.3  0.3  0.3  0.3  0.3  0.3  0.3                          ZnO   1.2    1.2    1.2  2.0  1.2  1.2  1.2  1.2  2.0                          BaO   2.5    2.5    2.5  2.5  4.0  2.5  2.5  2.5  2.5                          TiO.sub.2                                                                            3.3    3.3    3.3  3.3  3.3  3.3  3.3  3.3  3.3                          ZrO.sub.2                                                                            1.6    1.6    1.6  1.6  1.6  1.6  1.6  1.6  1.6                          As.sub.2 O.sub.3                                                                     0.8    0.8    0.8  0.8  0.8  0.8  0.8  0.8  0.8                          Fe.sub.2 O.sub.3                                                                     0.15   0.15   0.15 0.15 0.15 0.15 0.06 0.15 0.15                         V.sub.2 O.sub.5                                                                      0.2    0.2    0.2  0.2  0.2  0.2  0.2  0.2  0.2                          CeO.sub.2                                                                            0.2    --     --   0.2  --   0.2  --   --   0.2                          CaO   0.1    --     --   0.1  --   0.1  --   --   0.1                          SnO.sub.2                                                                            --     0.1    0.1  --   0.1  --   0.1  0.1  --                           ______________________________________                                               19     20      21   22    23   24    25   26                             ______________________________________                                         SiO.sub.2                                                                            66.0   66.9    64.9 64.3  65.3 66.0  66.0 67.2                           Al.sub.2 O.sub.3                                                                     19.0   19.0    20.0 20.0  20.0 20.0  20.0 20.0                           Li.sub.2 O                                                                           3.5    3.5     3.5  3.5   3.5  3.5   3.5  3.5                            Na.sub.2 O                                                                           0.3    0.3     0.4  0.4   0.4  0.4   0.3  0.4                            K.sub.2 O                                                                            0.3    0.3     0.6  0.6   0.6  0.6   0.4  0.6                            ZnO   2.0    1.2     0.8  0.8   0.8  0.8   0.8  0.8                            BaO   2.5    2.5     0.8  0.8   0.8  0.8   0.8  0.8                            TiO.sub.2                                                                            3.3    3.3     4.6  4.6   4.6  4.6   5.0  2.8                            ZrO.sub.2                                                                            1.6    1.6     1.6  1.6   1.6  1.6   1.6  1.6                            As.sub.2 O.sub.3                                                                     0.8    0.8     0.6  0.6   0.6  0.6   0.6  0.6                            Fe.sub.2 O.sub.3                                                                     0.15   0.15    0.15 0.15  0.15 0.15  0.1  0.1                            V.sub.2 O.sub.5                                                                      0.2    0.2     0.1  0.1   0.1  0.2   0.1  --                             CeO.sub.2                                                                            --     0.2     2.0  2.0   1.6  0.8   --   --                             CaO   --     --      --   0.6   --   --    --   --                             SnO.sub.2                                                                            0.1    --      --   --    --   --    0.8  --                             NiO   --     --      --   --    --   --    --   0.8                            WO.sub.3                                                                             --     --      --   --    --   --    --   0.8                            ______________________________________                                    

TABLE II recites the heat treatment schedules applied to the specimens of TABLE I in an electrically-heated furnace, a visual description of the crystallized glass-ceramic body, the predominant crystal phase present as identified through X-ray diffraction analysis, and the coefficient of thermal expansion (25°-700° C.) of the glass-ceramic body, where determined, utilizing measuring techniques conventional in the art. In each instance, the parent glass was heated to the first temperature level at about 100° C./hour, held at the first level to induce nucleation, the temperature raised to the second level at about 100° C./hour, held thereat to grow crystals on the nuclei, and then the crystallized body cooled to room temperature at furnace rate.

                  TABLE II                                                         ______________________________________                                         Ex-  Heat                            Coef. Exp.                                am-  Treatment   Visual     Crystal  (× 10.sup.-7 /                      ple  (°C.)                                                                               Appearance Phase    °C.)                               ______________________________________                                         1    780 for 1 hr.                                                                              Glossy,    β-Quartz                                                                           -3                                             900 for 1 hr.                                                                              black,     Solid                                                               transparent                                                                               Solution                                           1    780 for 1 hr.                                                                              Glossy,    β-Spodumene                                                                        --                                             1100 for 1 hr.                                                                             gray,      Solid                                                               opaque     Solution                                           2    780 for 1 hr.                                                                              Glossy,    β-Quartz                                                                           -1.9                                           900 for 1 hr.                                                                              black,     Solid                                                               translucent                                                                               Solution                                           2    780 for 1 hr.                                                                              Glossy,    β-Spodumene                                                                        10.5                                           1100 for 1 hr.                                                                             brown-beige,                                                                              Solid                                                               opaque     Solution                                           3    780 for 1 hr.                                                                              Brown-     β-Quartz                                                                           -1.5                                           900 for 1 hr.                                                                              black,     Solid                                                               translucent                                                                               Solution                                           3    780 for 1 hr.                                                                              Glossy,    β-Spodumene                                                                        13.3                                           1100 for 1 hr.                                                                             gray-beige,                                                                               Solid                                                               opaque     Solution                                           4    780 for 1 hr.                                                                              Black,     β-Quartz                                                                           -4.9                                           900 for 1 hr.                                                                              transparent                                                                               Solid                                                                          Solution                                           4    780 for 1 hr.                                                                              Glossy,    β-Spodumene                                                                        9.8                                            1100 for 1 hr.                                                                             gray-beige,                                                                               Solid                                                               opaque     Solution                                           5    780 for 1 hr.                                                                              Black,     β-Quartz                                                                           -6.8                                           900 for 1 hr.                                                                              transparent                                                                               Solid                                                                          Solution                                           5    780 for 1 hr.                                                                              Glossy,    β-Spodumene                                                                        8.9                                            1100 for 1 hr.                                                                             gray-beige,                                                                               Solid                                                               opaque     Solution                                           6    780 for 1 hr.                                                                              Black,     β-Quartz                                                                           -5.1                                           900 for 1 hr.                                                                              translucent                                                                               Solid                                                                          Solution                                           6    780 for 1 hr.                                                                              Glossy,    β-Spodumene                                                                        10.0                                           1100 for 1 hr.                                                                             gray-beige,                                                                               Solid                                                               opaque     Solution                                           7    780 for 1 hr.                                                                              Black,     β-Quartz                                                                           -4.0                                           900 for 1 hr.                                                                              translucent                                                                               Solid                                                                          Solution                                           7    780 for 1 hr.                                                                              Glossy,    β-Spodumene                                                                        10.3                                           1100 for 1 hr.                                                                             gray-beige,                                                                               Solid                                                               opaque     Solution                                           8    780 for 1 hr.                                                                              Black,     β-Quartz                                                                           -5.3                                           900 for 1 hr.                                                                              translucent                                                                               Solid                                                                          Solution                                           8    780 for 1 hr.                                                                              Glossy,    β-Spodumene                                                                        9.1                                            1100 for 1 hr.                                                                             gray-beige,                                                                               Solid                                                               opaque     Solution                                           9    780 for 1 hr.                                                                              Black,     β-Quartz                                                                           -3.0                                           900 for 1 hr.                                                                              translucent                                                                               Solid                                                                          Solution                                           9    780 for 1 hr.                                                                              Glossy,    β-Spodumene                                                                        11.0                                           1100 for 1 hr.                                                                             almond-    Solid                                                               beige,     Solution                                                            opaque                                                        10   780 for 1 hr.                                                                              Black,     β-Quartz                                                                           3.3                                            900 for 1 hr.                                                                              translucent                                                                               Solid                                                                          Solution                                           10   780 for 1 hr.                                                                              Glossy     β-Spodumene                                                                        15.2                                           1100 for 1 hr.                                                                             gray,      Solid                                                               opaque     Solution                                           11   780 for 1 hr.                                                                              Black,     β-Quartz                                                                           0.7                                            900 for 1 hr.                                                                              translucent                                                                               Solid                                                                          Solution                                           11   780 for 1 hr.                                                                              Glossy,    β-Spodumene                                                                        14.3                                           1100 for 1 hr.                                                                             yellow-    Solid                                                               almond,    Solution                                                            opaque                                                        12   780 for 1 hr.                                                                              Black,     β-Quartz                                                                           -2.7                                           900 for 1 hr.                                                                              translucent                                                                               Solid                                                                          Solution                                           12   780 for 1 hr.                                                                              Glossy,    β-Spodumene                                                                        9.7                                            1100 for 1 hr.                                                                             almond,    Solid                                                               opaque     Solution                                           13   780 for 1 hr.                                                                              Black,     β-Quartz                                                                           -1.9                                           900 for 1 hr.                                                                              translucent                                                                               Solid                                                                          Solution                                           13   780 for 1 hr.                                                                              Glossy,    β-Spodumene                                                                        --                                             1100 for 1 hr.                                                                             gray-beige,                                                                               Solid                                                               opaque     Solution                                           14   780 for 1 hr.                                                                              Black,     β -Quartz                                                                          1.4                                            900 for 1 hr.                                                                              translucent                                                                               Solid                                                                          Solution                                           14   780 for 1 hr.                                                                              Glossy,    β-Spodumene                                                                        15.5                                           1100 for 1 hr.                                                                             beige,     Solid                                                               opaque     Solution                                           15   780 for 1 hr.                                                                              Black,     β-Quartz                                                                           -1.6                                           900 for 1 hr.                                                                              translucent                                                                               Solid                                                                          Solution                                           15   780 for 1 hr.                                                                              Glossy,    β-Spodumene                                                                        12.8                                           1100 for 1 hr.                                                                             almond,    Solid                                                               opaque     Solution                                           16   780 for 1 hr.                                                                              Black,     β-Quartz                                                                           -1.2                                           900 for 1 hr.                                                                              translucent                                                                               Solid                                                                          Solution                                           16   780 for 1 hr.                                                                              Glossy,    β-Spodumene                                                                        4.8                                            1100 for 1 hr.                                                                             gray,      Solid                                                               opaque     Solution                                           17   780 for 1 hr.                                                                              Black,     β-Quartz                                                                           -2.5                                           900 for 1 hr.                                                                              translucent                                                                               Solid                                                                          Solution                                           17   780 for 1 hr.                                                                              Glossy,    β-Spodumene                                                                        11.9                                           1100 for 1 hr.                                                                             gray-beige,                                                                               Solid                                                               opaque     Solution                                           18   780 for 1 hr.                                                                              Black,     β-Quartz                                                                           -1.1                                           900 for 1 hr.                                                                              translucent                                                                               Solid                                                                          Solution                                           18   780 for 1 hr.                                                                              Glossy,    β-Spodumene                                                                        13.5                                           1100 for 1 hr.                                                                             almond,    Solid                                                               opaque     Solution                                           19   780 for 1 hr.                                                                              Black,     β-Quartz                                                                           -2.8                                           900 for 1 hr.                                                                              translucent                                                                               Solid                                                                          Solution                                           19   780 for 1 hr.                                                                              Glossy,    β-Spodumene                                                                        11.9                                           1100 for 1 hr.                                                                             gray-beige,                                                                               Solid                                                               opaque     Solution                                           20   780 for 1 hr.                                                                              Black,     β-Quartz                                                                           -2.4                                           900 for 1 hr.                                                                              translucent                                                                               Solid                                                                          Solution                                           20   780 for 1 hr.                                                                              Glossy,    β-Spodumene                                                                        11.0                                           1100 for 1 hr.                                                                             almond,    Solid                                                               opaque     Solution                                           21   780 for 1 hr.                                                                              Black-     β-Quartz                                                                           0.9                                            900 for 1 hr.                                                                              brown,     Solid                                                               translucent                                                                               Solution                                           21   780 for 1 hr.                                                                              Glossy,    β-Spodumene                                                                        11.7                                           1100 for 1 hr.                                                                             beige,     Solid                                                               opaque     Solution                                           22   780 for 1 hr.                                                                              Black-     β-Quartz                                                                           --                                             900 for 1 hr.                                                                              brown,     Solid                                                               translucent                                                                               Solution                                           22   780 for 1 hr.                                                                              Glossy,    β-Spodumene                                                                        --                                             1100 for 1 hr.                                                                             yellow,    Solid                                                               opaque     Solution                                           23   780 for 1 hr.                                                                              Black-brown,                                                                              β-Quartz                                                                           --                                             900 for 1 hr.                                                                              translucent                                                                               Solid                                                                          Solution                                           23   780 for 1 hr.                                                                              Glossy,    β -Spodumene                                                                       --                                             1100 for 1 hr.                                                                             beige,     Solid                                                               opaque     Solution                                           24   780 for 1 hr.                                                                              Black-     β-Quartz                                                                           -1.5                                           900 for 1 hr.                                                                              brown,     Solid                                                               translucent                                                                               Solution                                           24   780 for 1 hr.                                                                              Glossy,    β-Spodumene                                                                        13.3                                           1100 for 1 hr.                                                                             gray-beige,                                                                               Solid                                                               opaque     Solution                                           25   780 for 1 hr.                                                                              Black,     β-Quartz                                                                           -0.5                                           900 for 1 hr.                                                                              opaque     Solid                                                                          Solution                                           25   780 for 1 hr.                                                                              Glossy,    β-Spodumene                                                                        12.8                                           1100 for 1 hr.                                                                             blue,      Solid                                                               opaque     Solution                                           26   780 for 1 hr.                                                                              Ruby,      β-Quartz                                                                           --                                             900 for 1 hr.                                                                              transparent                                                                               Solid                                                                          Solution                                           26   780 for 1 hr.                                                                              Glossy,    β-Spodumene                                                                        10.4                                           1100 for 1 hr.                                                                             light blue,                                                                               Solid                                                               opaque     Solution                                           ______________________________________                                    

TABLE III records a summary of the general trends in colors and optical transmissions produced in the inventive glass-ceramic bodies as a function of compositional variations. It must be emphasized that the descriptions provided represent trends only and assume precursor glasses having base compositions within the above-cited regimes. As reported, "higher" values reflect amounts of a component at the higher end of the operable range thereof and "lower" values the other extreme of the range. The "lower" values of the "color package" ingredients V₂ O₅, CeO₂ CaO, and SnO₂ signify the virtual absence thereof.

                  TABLE III                                                        ______________________________________                                                   Beta-Quartz       Beta-Spodumene                                     Component Solid Solution    Solid Solution                                     ______________________________________                                         High Al.sub.2 O.sub.3                                                                    Haze develops     Greater gray                                                                   color, thermal                                                                 expansion rises                                    Low Al.sub.2 O.sub.3                                                                     Translucency develops,                                                                           Greater yellow-                                              blacker color     beige color                                        High Li.sub.2 O                                                                          Blacker color, opacity                                                                           Greater gray                                                 develops          color                                              Low Li.sub.2 O                                                                           Greater transparency,                                                                            Greater yellow                                               browner color     color                                              High ZnO  Blacker color, opacity                                                                           Greater beige                                                develops          color                                              Low ZnO   Browner color, greater                                                                           Greater gray                                                 transparency      color                                              High BaO  Blacker color, opacity                                                                           Greater beige                                                develops          color                                              Low BaO   Greater transparency,                                                                            Greater grayer                                               browner color     color                                              High TiO.sub.2                                                                           Blacker color, opacity                                                                           Greater beige                                                develops          color, thermal                                                                 expansion rises                                    Low TiO.sub.2                                                                            Greater transparency,                                                                            Greater gray                                                 browner color     color                                              High ZrO.sub.2                                                                           Browner color     Greater beige                                                                  color                                              Low ZrO.sub.2                                                                            Greater gray color                                                                               Greater gray                                                                   color, satin                                                                   surface develops                                   High As.sub.2 O.sub.3                                                                    Blacker color, opacity                                                                           Greater beige                                                develops          color                                              Low As.sub.2 O.sub.3                                                                     Greater transparency,                                                                            Greater gray                                                 greater amber color                                                                              color                                              High Na.sub.2 O                                                                          Slightly greater brown                                                                           Slightly greater                                             color             beige color                                        Low Na.sub.2 O                                                                           Slightly greater black                                                                           Slightly greater                                             color             gray color                                         High K.sub.2 O                                                                           Slightly greater brown                                                                           Slightly greater                                             color             beige color                                        Low K.sub.2 O                                                                            Slightly greater black                                                                           Slightly greater                                             color             gray color                                         High Fe.sub.2 O.sub.3                                                                    Blacker color,    Greater beige                                                translucency develops                                                                            color                                              Low Fe.sub.2 O.sub.3                                                                     Greater transparency,                                                                            Greater gray                                                 browner color     color, thermal                                                                 expansion falls                                    High V.sub.2 O.sub.5                                                                     Blacker color,    Greater black-                                               translucency develops                                                                            gray color                                         Low V.sub.2 O.sub.5                                                                      Greater transparency,                                                                            Greater beige                                                browner color     color                                              High CeO.sub.2                                                                           Blacker color,    Greater beige                                                translucency develops                                                                            color                                              Low CeO.sub.2                                                                            Greater transparency,                                                                            Greater gray                                                 browner color     color                                              High CaO  Blacker color,    Greater beige-                                               translucency develops                                                                            yellow color                                       Low CaO   Greater transparency,                                                                            Greater gray                                                 browner color     color                                              High SnO.sub.2                                                                           Blacker color,    Greater gray                                                 translucency develops                                                                            color                                              Low SnO.sub.2                                                                            Greater transparency,                                                                            Greater beige                                                brown color       color                                              ______________________________________                                     

I claim:
 1. A transparent, translucent, or opaque glass-ceramic article exhibiting colors ranging from black to brown to red and containing β-quartz solid solution as the predominant crystal phase, said glass-ceramic article being essentially free from MgO and consisting essentially, expressed in terms of weight percent on the oxide basis, of:

    ______________________________________                                         SiO.sub.2                                                                               63.5-69      BaO     0-5                                              Al.sub.2 O.sub.3                                                                        15-25        TiO.sub.2                                                                              >2.5-6                                           Li.sub.2 O                                                                              2.5-4        ZrO.sub.2                                                                              0-2                                              Na.sub.2 O                                                                              0.1-0.6      As.sub.2 O.sub.3                                                                       0.4-0.8                                          K.sub.2 O                                                                               0.1-0.6      Fe.sub.2 O.sub.3                                                                       0.05-0.2                                         ZnO      0-2                                                                   ______________________________________                                    

and 0.3-3% total of at least two oxides in the indicated proportions selected from the group of 0-2% CaO, 0-3% CeO₂, 0-1% NiO, 0-1.5% SnO₂, 0-0.3% V₂ O₅, and 0-1% WO₃.
 2. A glass-ceramic article according to claim 1 also containing up to 3% total of at least one oxide selected from the group of B₂ O₃, Cr₂ O₃, Cs₂ O, Cu₂ O, La₂ O₃, MnO, and Nb₂ O₅, wherein the individual value of each oxide is below 1%.
 3. An opaque glass-ceramic article exhibiting colors ranging from gray to brown to almond to beige to yellow to blue and containing β-spodumene as the predominant crystal phase, said glass-ceramic article being essentially free from MgO and consisting essentially, expressed in terms of weight percent on the oxide basis, of:

    ______________________________________                                         SiO.sub.2                                                                               63.5-69      BaO     0-5                                              Al.sub.2 O.sub.3                                                                        15-25        TiO.sub.2                                                                              >2.5-6                                           Li.sub.2 O                                                                              2.5-4        ZrO.sub.2                                                                              0-2                                              Na.sub.2 O                                                                              0.1-0.6      As.sub.2 O.sub.3                                                                       0.4-0.8                                          K.sub.2 O                                                                               0.1-0.6      Fe.sub.2 O.sub.3                                                                       0.05-0.2                                         ZnO      0-2                                                                   ______________________________________                                    

and 0.3-3% total of at least two oxides in the indicated proportions selected from the group of 0-2% CaO, 0-3% CeO₂, 0-1% NiO, 0-1.5% SnO₂, 0-0.3% V₂ O₅, and 0-1% WO₃.
 4. A glass-ceramic article according to claim 3 also containing up to 3% total of at least one oxide selected from the group of B₂ O₃, Cr₂ O₃, Cs₂ O, Cu₂ O, La₂ O₃, MnO, and Nb₂ O₅, wherein the individual value of each oxide is below 1%. 